1. Field of the Invention
The invention relates to a speed reduction unit and a pump, in general, and, in particular, to an integrated speed reducer and pump assembly.
2. Description of Related Art
Oil pumps are widely used in vehicles of all types to provide pressurized oil flow for lubrication or for hydraulic actuation. Conventional oil pumps for vehicles are connected directly or indirectly through gears, chains or belts to the main shafts of engines for such vehicles. The rotational speeds of these pumps are in direct proportion to the engine speeds. Therefore, as engine speed increases under demanded power, the speed of a pump also increases, causing output oil pressure of the pump to increase. At higher engine speeds, the oil pressure may increase to undesirable levels. To overcome this situation, pressure relief valves are often provided in pump systems to relieve the pressure and direct the excess oil back to the pumps. However, energy is lost in this process. Thus, disconnecting an oil pump from the main drive shaft of an engine is highly desirable.
An attractive means to provide an independently powered oil pump is to electrify the pump, driving the pump independently with an electric motor. There are many advantages using electrified oil pump. For example, in an engine oil pump application an electric pump can provide lubricant to vital parts prior to engine start and/or after engine shutdown, thus extending engine life. In addition, it can adaptively regulate lubricant flow to suit various operating conditions and, as a result, improve engine performance.
However, to provide adequate power level to drive an oil pump, an electric motor usually has to run at elevated speeds to conserve motor size. Consequently, a separate speed reduction unit connecting the oil pump and electric motor is often necessary, acting as a torque multiplier. Unfortunately, the addition of a speed reduction unit requires additional space. Therefore, there is a need to integrate a speed reducer with an oil pump.